1. Field of the Invention
This invention relates generally to a solid state color television camera, and is directed more particularly to a solid state color television camera in which color difference signals obtained from a special color filter in a line sequential manner are converted to a simultaneous color signal.
2. Description of the Prior Art
In the art there have been proposed various solid state color television cameras which use a semiconductor element such as a bucket brigade device (BBD), charge coupled device (CCD) or the like as its solid state image sensing device. Similarly, various color filters which are disposed at the front of the solid state image sensing device have been well known. One of the well known color filters, for example, a so-called double-green type filter, which includes much amount of a green color component, especially appealing to a view's eyesight, than those of the other color components forming the luminance signal, is used to improve the resolution.
This double-green type color filter has a plurality of transparent or light transmissibility regions whose unit region corresponds to one picture element. In this case, the region corresponding to an odd horizontal scanning line is so selected that it contains the green color component G twice as compared with red and blue color components R and B, for example, the transparent regions of G, R and B are arranged in the horizontal scanning line in the order of G-R-G-B which is repeated sequentially in this order.
On an even horizontal scanning line, due to the signal process described later, the position of the transparent regions is so selected that the green color component G is reverse in phase to that on the odd horizontal scanning line.
Accordingly, when an object is picked up by a camera using the above filter, the spectra and phase relation of the respective color components become as follows.
If the sampling frequency in the horizontal scanning direction is selected as f.sub.C and the band of green color component G is selected as sampling frequency f.sub.C (4.5 MH.sub.z), the sampling output relating to the green signal in the output obtained from the solid state image sensing device includes, in addition to a modulating signal component (DC components or base band components) S.sub.DG, a side band component (AC component) S.sub.MG whose carrier is sampling frequency f.sub.C. If sampling frequency f.sub.C is about 4.5 MH.sub.z as set forth above, the relation of the signal bands becomes such that side band component S.sub.MG is mixed into modulating signal component S.sub.DG to cause a sampling error. This sampling error caused by side band component S.sub.MG deteriorates a reproduced picture, so that in general the sampling error is removed by utilizing the vertical correlation process or theory. That is, since the phases of carries obtained from adjacent horizontal scanning lines are opposite, the sampling error can be removed by the vertical correlation process.
The carriers of the respective red color component R and blue color component B are just one-half of that of green color component G, so that it is impossible that even if components R and B are obtained from the respective horizontal scanning lines, side band components S.sub.MR (S.sub.MB) are removed by the vertical correlation process as in green component G, since the phases of their carriers are not opposite.
In order to remove bad affect of the side band components on a reproduced picture, it is difficult or almost impossible to limit the pass band of the wave length of only a desired color signal by an optical device, that is, to form a optical low pass filter of the type depending upon the wave length.